Effect of silicon content on microstructure, mechanical and electrical properties of the directionally solidified Al-based quaternary alloys

Effect of silicon content on the microstructure (lamellar and flake), mechanical (microhardness, ultimate tensile strength) and electrical resistivity properties of Al-Cu-Fe-Si quaternary alloys has been investigated. Al-26Cu-0.5Fe-xSi (x = 6.5, 8, 10, 12 and 14 wt %) were prepared using metals of 99.99% high purity in the vacuum atmosphere. These alloys were directionally solidified under constant temperature gradient (8.50 K/mm) and growth rate (8.25 μm/s) by using a Bridgman-type directional solidification furnace. Eutectic spacing, microhardness, ultimate tensile strength and electrical resistivity were expressed as functions of composition. The dependency of the eutectic spacing, microhardness, tensile strength and electrical resistivity on the composition (Si content) were determined. According to experimental results, the microhardness, ultimate tensile strength and electrical resistivity of the solidified samples increase with increasing the Si content, but decrease eutectic spacing. Variation of electrical resistivity with the temperature in the range of 300-650 K for studied alloys was also measured by using a standard d.c. four−point probe technique.